How can I tell Opera the correct encoding for a page?

All the other browsers on my Macbook Pro have a View -> Text Encoding menu that lets me correct an incorrect encoding of a page, but Opera (no longer) seems to have this ability. For an example of a page that can't be displayed correctly in Opera, try:http://www.zein.se/patrick/3000char.html

The problem with this page is that, although its HTML header contains the correct encoding (GB2312), the HTTP headers declare it to be charset=iso-8859-1, which gives Latin1 gibberish instead of the Chinese characters. The owner of the page probably can't correct this, because fixing the HTTP headers requires permission to change the web server's config files.

The same gibberish shows up on a few other browsers, but I can fix it in the browsers' menus, but this doesn't work with Opera. Some browsers handle it correctly, by using the HTML header's charset declaration when the two conflict. Also, I copied the page to my own web site, where I could tell the server to not send the charset= field in the Content-Type HTTP header. It displays correctly in Opera, showing that Opera does understand the HTML header charset and will use it if the HTTP headers don't declare a charset. (But my copy of the page won't contain updates to the original, so I'd rather make the browser handle it correctly).

So is there any way to persuade Opera to override the incorrect charset in the HTTP headers in cases like this? Or is there some way to change Opera's charset by hand for a single page, as can be done with most other browsers that I've seen?

(The best solution would be to update Opera to ignore the HTTP header charset in cases like this. But having a menu item to force a charset for a page would be very useful to those of us doing a lot of web testing.)